Roll fuser

ABSTRACT

A contact fuser assembly for use in an electrostatic reproducing apparatus including an internally heated metal core cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are moved with the toner images contacting the metal core. The fuser assembly is characterized by the provision of a sump of release agent material which material coats the fuser roll structure. A polymer covered cleaning member immersed in a mini-sump containing some of the release agent material contacts the fuser roll structure for removing nonvisual toner and other contaminates offset thereto during the reproduction process. The mini-sump is removably disposed in a larger sump and serves to prevent contamination of the main sump.

United States Patent [1 1 Thettu 1 1 ROLL FUSER [75] Inventor:Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Jan. 2, 1975 211 Appl. No.2 537,881

[ Dec. 30, 1975 3,811,821 5/1974 Ariyama ct al. 118/60 PrimaryExaminerMervin Stein Assistant ExaminerDouglas Salser 57 ABSTRACT Acontact fuser assembly for use in an electrostatic reproducing apparatusincluding an internally heated metal core cooperating with a resilientbackup roll to form a nip through which substrates carrying toner imagesare moved with the toner images contacting the metal core. The fuserassembly is characterized by the provision of a sump of release agentmaterial which material coats the fuser roll structure. A polymercovered cleaning member immersed in a mini-sump containing some of therelease agent material contacts the fuser roll structure for removingnon-visual toner and other contaminates offset thereto during thereproduction process. Themini-sump is removably disposed in a largersump and serves to prevent contamination of the main sump.

'-7 Claims, 1 Drawing Figure US. Patent Dec. 30, 1975 3,929,094

ROLL FUSER BACKGROUND OF THE INVENTION This invention relates generallyto xerographic copying apparatus and, more particularly, to a contactfusing system and cleaning mechanism therefor for fixing electroscopictoner material to a support member.

In the process of xerography, a light image of an original to be copiedis typically recorded in the form of a latent electrostatic image upon aphotosensitive member with subsequent rendering of the latent imagevisible by the application of electroscopic marking particles, commonlyreferred to as toner. The visual image can be either fixed directly uponthe photosensitive member or transferred from the member to a sheet ofplain paper with subsequent affixing of the image thereto.

In order to permanently affix or fuse electroscopic toner material ontoa support member by heat, it.is necessary to elevate the temperature ofthe toner material to a point at which the constituents of the tonermaterial coalesce and become tacky. This action causes the toner to beabsorbed to some extent into the fibers of the support member which, inmany instances, constitutes plain paper. Thereafter, as the tonermaterial cools, solidification of the toner material occurs causing thetoner material to be firmly bonded to the support member. In both thexerographic as well as the electrographic recording arts, the use ofthermal energy for fixing toner images onto a support member is old andwell known.

One approach to thermal fusing of electroscopic toner images onto asupport has been to pass the support with the toner images thereonbetween a pair of opposed roller members, at least one of which isinternally heated. During operation of a fusing system of this type, thesupport member to which the toner images are electrostatically adheredis moved through the nip formed between the rolls with the toner imagecontacting the heated roll to thereby effect heating of the toner imageswithin the nip. By controlling the heat transferred to the toner,virtually no offset of the toner particles from the copy sheet to thefuser roll is experienced under normal conditions. This is because theheat applied to the surface of the roller is insufficient to raise thetemperature of the surface of the roller above the hot offsettemperature of the toner whereat the toner particles in the image areasof the toner would liquify and cause a splitting action in the moltentoner to thereby result in hot offset. Splitting occurs when thecohesive forces holding the viscous toner mass together are less thanthe adhesive forces tending to offset it to a contacting surface such asa fuser roll.

However, toner particles will be offset to the fuser roll by aninsufficient application of heat to the surface thereof (i.e. coldoffsetting); by imperfections in the properties of the surface of theroll; or by the toner particles insufficiently adhering to the copysheet by the electrostatic forces which normally hold them there. Insuch a case, toner particles may be transferred to the surface of thefuser roll with subsequent transfer to the backup roll during periods oftime when no copy paper is in the nip.

Moreover, toner particles can be picked up by the fuser and/or backuproll during fusing of duplex copies or simply from the surroundings ofthe reproducing apparatus.

One arrangement for minimizing the problems attendant the foregoing,particularly that which is commonly referred to as offsetting has beento provide a fuser roll with an outer surface or covering ofpolytetrafluoroethylene, commonly known as Teflon, to which a releaseagent such as silicone oil is applied, the thickness of the Teflon beingon the order of several mils and the thickness of the oil being lessthan 1 micron. Silicone based oils, which possess a relatively lowsurface energy, have been found to be materials that are suitable foruse in the heated fuser roll environment where Teflon constitutes theouter surface of the fuser roll. In practice, a thin layer of siliconeoil is applied to the surface of the heated roll to thereby form aninterface between the roll surface and the toner images carried on thesupport material. Thus a low surface energy layer is presented to thetoner as it passes through the fuser nip and thereby prevents toner fromoffsetting to the fuser roll surface. The foregoing notwithstanding,non-visual offsetting (i.e. offsetting of very fine particles of toner)does occur. In prior art constructions (fuser structures where the outersurface comprises Teflon or silicone rubber) such offsetting has beencombated by the employment of various cleaning members, the wickmaterial employed for applying the silicone based oil to the fuser rollserving this purpose.

However, it has been found that cleaning systems which are known to workwith the aforementioned types of fuser roll surfaces are not acceptablefor utilization with metal roll fusers.

Accordingly, the primary object of this invention is to provide a newand improved contact fuser system for fixing toner images to substrates.

A more particular object of this invention is to provide a fuserroll-cleaning structure for utilization with a metal roll fuser.

Another object of this invention is to provide a contact fuser systememploying a metal fuser roll structure and a sump of release agentmaterial wherein a cleaning memb'rfor said fuser roll structure isimmersed in a mini-sump containing some of the release agent, themini-sump being removable from a main sump and serving to preventcontamination of the main sump.

BRIEF OF THE INVENTION Briefly, the above-cited objects are accomplishedby the provision of a contact fuser apparatus comprising a metal fuserroll structure cooperating with a resilient backup roll to form a nipthrough which substrates carrying toner images are passed with the tonerimages contacting the fuser roll structure.

A sump of release agent material, preferably polyethylene, is providedfor coating the fuser roll structure to enhance the release of tonerparticles and other contaminates from the surface of the fuser rollstructure. A polymer coated cleaning roll structure which is supportedadjacent the fuser roll structure and rotated thereby is immersed in amini-sump containing some of the polyethylene release agent material.The mini-sump is removably disposed in the main sump and preventscontamination thereof.

The cleaning roll is coated with a polymer which at the operatingtemperatures of the fuser apparatus is in a tacky state, in whichcondition, together with the aid of the release agent material is usefulin cleaning toner and other contaminates from the fuser roll structure.

3 Other objects and advantages of the present invention will becomeapparent when read in conjunction with the accompanying drawing.

DESCRIPTION OF THE DRAWING The FIGURE is a side elevational view of acontact fuser representing the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Since the xerographicreproducing process is well known, a detailed description thereof isomitted. For those who would consider a description of the xerographicprocess necessary for a complete understanding of the present inventionreference may be had to US. Pat. Nos. 3,718,116 and 3,745,972.

As shown in the FIGURE the present invention comprises a fuser assembly15 including a heated roll structure 30 including a hollow cylinder orcore 31 having a suitable heating element 32 disposed in the hollowportion thereof which is coextensive with the cylinder. The heatingelement 32 may comprise any suitable type heater for elevating thesurface temperature of the cylinder to operational temperatures,therefore, 250400F. For example, it may be a quartz lamp. The cylinderor core 31 is fabricated from any suitable material capable ofaccomplishing the objects of the present invention. Typical materialsare copper, anodized aluminum and alloys thereof, steel, stainlesssteel, nickel and alloys thereof, nickel plated copper and chrome platedcopper. The resulting structure has an outside diameter on the order of1.5 to 3.0 inches and has a length on the order of to inches. Powerrequirements for the foregoing are 500-2500 watts peak power with anaverage power of 300-2000 watts and 75-250 watts for standby.

The surface temperature of the fuser roll structure is controlled bycontacting the surface thereof with a thermistor probe 45 in a mannerdescribed in US. Pat. No. 3,327,096, issued in 1967 to Bernous andincorporated herein by reference.

The fuser assembly 15 further comprises a backup roll structure 33 whichcooperates with the fuser roll structure to form a nip 34 through whicha copy paper or substrate 35 passes such that toner images 36 thereoncontact the fuser roll structure. The backup roll structure may compriseany suitable construction, for example, a steel cylinder, but preferablycomprise a rigid steel core 37 having a Viton elastomer surface or layer38 thereon. A suitable roll has a core approximately 1.8 inches indiameter with a 0.1 inch cover or layer structure of Viton elastomer orother suitable high temperature elastomeric layer structure, forexample, silicone rubber and a combination of Viton or silicone rubberwith Teflon thereon. Viton is a trademark of the E. I. duPont de Nemoursand Company. The specific dimensions of the members making up the backuproll will be dictated by the requirements of the particular copyingapparatus wherein the fuser assembly 15 is employed, the dimensionsbeing greater or less depending upon the process speed of the machine.The heated roll and backup roll structures may be mounted on fixed axes,therefore not requiring movement in and out of engagement or they may bemounted in accordance with prior art devices wherein the backup roll ismoved into and out of engagement with the fuser roll structure.

Means (not shown) for applying a loading force in a conventional mannerto the fuser assembly 15 serves to create nip pressures on the order of15 to 150 psi average. The durometer of the backup roll is chosen suchthat dwell times of 5 to milliseconds can be obtained with loadingforces within the aforementioned range of pressures. Dwell time isproportional to the ratio of the nip length to the surface speed of therolls. For a given angular velocity the surface speeds will varydepending upon the diameter of the rolls. For example, with a 2 inchfuser roll, speeds of 0 to 30 inches per second are attainable and for a3 inch fuser roll, speeds of O to 45 inches per second have beenattained. Accordingly, it can be seen that the aforementioned dwelltimes can be obtained by varying one or the other or both of the dwelltime relationships. Durometers of 20-90 Shore A have been found toprovide satisfactory results.

The aforementioned materials from which the fuser roll structure 30 maybe fabricated are relatively high surface energy materials,consequently, hot toner material contacting such surfaces would readilywet the surface of the fuser roll. Accordingly, there is provided a mainsump 39 for containing release material 40 capable of interacting withthe fuser roll. The release material is preferably a low molecularweight material which is solid at room temperature and which has arelatively low viscosity at the operating temperatures of the fuser rollstructure. An example of such a material is polyethylene hopolymermanufactured by Allied Chemical Co. and having the designation AC-8hopolymer. A resistance heater 38 which may be of the brush-on film typeis provided for melting the polyethylene.

A metering blade 41 preferably of silicone rubber is mounted to the sump39 by conventional means such that an edge 42 thereof contacts the fuserroll structure serving to meter the release agent 40 in its liquid stateonto the fuser roll. In the preferred embodiment, a blade 0.060 inchthick and having a width of 1.0 inch and length of 15 inches has beenemployed. By means of such a construction a 0.1-0.5 micron thickness ofrelease agent is applied to the surface of the fuser roll.

A pair of end seals 47, preferably of sponge rubber are provided tocontain a release agent material in the sump 39. One or more stripperfingers 50 are provided for insuring removal of the substrate from thefuser roll.

Although the interaction of the polyethylene material with the surfaceof the fuser roll structure is not well understood, it is believed thata thermal degradation of the polyethylene takes place to form aby-product of carboxylic acid which chemically reacts with the surfaceof the fuser roll structure. It has been noted that where thepolyethylene and the fuser roll surface form a boundary layer with theambient air, beading of the surface of the fuser roll structure takesplace along such boundary. Accordingly, a wiper blade 60 is supportedadjacent to the sump 39 in any suitable manner such that it contacts thecore 31 to form a wiper blade/- polyethylene/air boundary 62 and therebyprevent the formation of a core/polyethylene/air boundary which wouldresult in the aforementioned formation of a bead on the core which wouldprint out on the copy sheets 14 and also disrupt proper operation of thecombination seal and metering blade 41. The wiper blade 60 is preferablyfabricated from a material which is compatible with the polyethylene(i.e. does not chemically react therewith and to a lesser degree isdimensionally stable in the presence thereof). To this end, the wiperblade comprises an elastomeric material, for example, silicone rubber.

In accordance with the objects of the present invention, a cleaning rollstructure 64 is positioned to clean the fuser roll structure 30 of papercontamination and non-visual offset as well as visual toner offsetparticles. The cleaning roll structure comprises a metal core member 66which is covered by a cylindrical sleeve member 68 made of polyesterpolymer material. Any suitable polyester polymer material having amelting or softening point ranging from about 120 to about 275C can beemployed. Typical materials are aliphatic, aromatic or mixtures ofaliphatic, aromatic polyesters. Examples of these classes of materialsare polyethylene oxolate, poly-pp xylelene terephthalate,polyethylene/neopentyl terephthalate. Preferred materials of the mixedclass of polyesters are PE-IOO or PE-ZOO, trademarks of GoodyearCompany, of Akron, Ohio. The sleeve member 68 has a thickness of about0.005 to about 0.030 inches. The sleeve member may be applied to themetal core member 66 by any suitable technique such as solvent spraying,extrusion wrapping, hot melt rolling or combinations thereof. Preferablythe final application is by heat shrinking the extruded polyester tubeover the core member. Desirably, hot rolling is applied during the heatshrinking process.

It has been found that paper contamination on the fuser roll structure30 is physically attracted to the sleeve 68 due to good adhesion at hightemperature. The viscosity of the polyester material is such that it hashigh elongation at the operating temperatures coupled with excellentwetting properties.

Any loose paper fiber and/or background toner particles attracted by thefuser roll surface collect thereon and transfer to the sleeve member 68by virtue of the physical adhesion of the contamination to the polyesterpolymer material. As can be observed from the FIG- URE of the drawing,the cleaning roll member 64 is immersed in the polyethylene releaseagent material. it has been found that the adhesion action of thepolymer material along with the action of the polyethylene release agentmaterial effectively removes the toner material and other contaminatesfrom the fuser roll structure. However, the cooperative action is notunderstood. Cleaning of metal fuser rolls was attempted with a cleaningmember such as the roll member 64 which was not immersed in the releaseagent. The foregoing yielded unacceptable results.

The cleaning roll member 64 is disposed in a minisump structure 70 whichis removably disposed in a conventional means (not shown) within thevolume delineated by the main sump 39. It will be appreciated 6 thatcontaminates removed from the fuser roll structure 30 will accumulate inthe release agent material contained in the mini-sump and will,therefore, minimize the contamination of the main sump. Accordingly, therelease agent material which is utilized for coating the fuser rollstructure 30 and supplied from the main sump 39 is highly effective forits intended purpose since it is substantially free of deleteriouscontaminates.

While the invention has been shown and described in conjunction with thepreferred embodiment thereof, it will be understood that variousmodifications thereto may be made by those skilled in the art withoutdeparting from the spirit of the invention and such modifications areintended to be covered by the claims appended hereto.

What is claimed is:

l. Fuser apparatus for fixing toner images to support members, saidapparatus comprising:

a heated metal fuser member;

a resilient member cooperating with said metal fuser member to form anip through which said support members pass in order to soften saidtoner images;

a first sump containing release agent material to .be

coated on said metal fuser member;

a second sump smaller in size than said first sump and disposed withinan area delineated by said first sump, said second sump also containingrelease agent material; and

means for cleaning toner particles from said fuser members, saidcleaning member being disposed in said second sump whereby the tonerparticles removed from said fuser member are prevented fromcontaminating the release agent material contained in said first sump.

2. Apparatus according to claim 1, wherein said second sump is removablydisposed within said area.

3. Apparatus according to claim 2, wherein said cleaning membercomprises a polymer material on the surface thereof that is tacky at theoperating temperature of the fuser apparatus.

4. Apparatus according to claim 3, wherein said release agent materialcomprises polyethylene.

5. Apparatus according to claim 4, wherein said fuser member isinternally heated and said support member moves through said nip withsaid toner images contacting said fuser member.

6. Apparatus according to claim 5, wherein said members comprise rollstructures.

7. Apparatus according to claim 6, wherein said fuser member comprises acopper outer surface.

i l l l l

1. Fuser apparatus for fixing toner images to support members, saidapparatus comprising: a heated metal fuser member; a resilient membercooperating with said metal fuser member to form a nip through whichsaid support members pass in order to soften said toner images; a firstsump containing release agent material to be coated on said metal fusermember; a second sump smaller in size than said first sump and disposedwithin an area delineated by said first sump, said second sump alsocontaining release agent material; and means for cleaning tonerparticles from said fuser members, said cleaning member being disposedin said second sump whereby the toner particles removed from said fusermember are prevented from contaminating the release agent materialcontained in said first sump.
 2. Apparatus according to claim 1, whereinsaid second sump is removably disposed within said area.
 3. Apparatusaccording to claim 2, wherein said cleaning member comprises a polymermaterial on the surface thereof that is tacky at the operatingtemperature of the fuser apparatus.
 4. Apparatus according to claim 3,wherein said release Agent material comprises polyethylene.
 5. Apparatusaccording to claim 4, wherein said fuser member is internally heated andsaid support member moves through said nip with said toner imagescontacting said fuser member.
 6. Apparatus according to claim 5, whereinsaid members comprise roll structures.
 7. Apparatus according to claim6, wherein said fuser member comprises a copper outer surface.